The present invention relates to the detection of flaws in wire as that wire passes through a drawing die.
A paper by T. Sato et al entitled `Assessment of Frictional Conditions by Acoustic-Emission Technique in Metal Forming` appearing in the Journal of the Japanese Society for Technology of Plasticity 21 (1980) 608-613 refers to laboratory experiments on the monitoring of acoustic emission during sheet-and wire-drawing of aluminum, and concludes that this approach has potential for detecting changes in the frictional conditions at the die/wire interface resulting from interruption in the supply of lubricant or wear of the die. Two types of sensors were used, one having a resonance frequency of 23 kHz and characteristic in the range 200 Hz to 15 kHz, and the other having a resonance frequency of 300 kHz. However, this approach is suited only for detecting the aforementioned changes and does not give discernible information about any physical properties of the wire being drawn. Yet, experience has shown that the wire, or a section thereof, may be useless by including a flaw that goes undetected when the above monitoring is used.